If you drill the hole slightly larger than the screw you attach it with, then put a piece of fuel tubing in the hole and then put your screw in. The fuel tubing will act as a "shock absorber" and isolate the cowl from the vibrations. A little bit of nyrod inserted in the wood also helps to keep the screw from vibrating back out. see attached diagram. I've done more cowls like this than I can count and it works every time.

Hope this helps

ken